/*
 * ArrayInstance.java January 2007
 *
 * Copyright (C) 2007, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.core;

import java.lang.reflect.Array;

import wx.xml.simpleframework.xml.strategy.Value;

/**
 * The <code>ArrayInstance</code> object is used for creating arrays
 * from a specified <code>Value</code> object. This allows primitive
 * and composite arrays to be acquired either by reference or by value
 * from the given value object. This must be  given the length of the
 * array so that it can be allocated correctly.
 *
 * @author Niall Gallagher
 * @see wx.xml.simpleframework.xml.core.Instance
 */
class ArrayInstance implements Instance {

    /**
     * This is the value object that contains the criteria.
     */
    private final Value value;

    /**
     * This is the array component type for the created array.
     */
    private final Class type;

    /**
     * This is the length of the array to be instantiated.
     */
    private final int length;

    /**
     * Constructor for the <code>ArrayInstance</code> object. This
     * is used to create an object that can create an array of the
     * given length and specified component type.
     *
     * @param value this is the value object describing the instance
     */
    public ArrayInstance(Value value) {
        this.length = value.getLength();
        this.type = value.getType();
        this.value = value;
    }

    /**
     * This method is used to acquire an instance of the type that
     * is defined by this object. If for some reason the type can
     * not be instantiated an exception is thrown from this.
     *
     * @return an instance of the type this object represents
     */
    public Object getInstance() throws Exception {
        if (value.isReference()) {
            return value.getValue();
        }
        Object array = Array.newInstance(type, length);

        if (value != null) {
            value.setValue(array);
        }
        return array;
    }

    /**
     * This method is used acquire the value from the type and if
     * possible replace the value for the type. If the value can
     * not be replaced then an exception should be thrown. This
     * is used to allow primitives to be inserted into a graph.
     *
     * @param array this is the array to insert as the value
     * @return an instance of the type this object represents
     */
    public Object setInstance(Object array) {
        if (value != null) {
            value.setValue(array);
        }
        return array;
    }

    /**
     * This is the type of the object instance that will be created
     * by the <code>getInstance</code> method. This allows the
     * deserialization process to perform checks against the field.
     *
     * @return the type of the object that will be instantiated
     */
    public Class getType() {
        return type;
    }

    /**
     * This is used to determine if the type is a reference type.
     * A reference type is a type that does not require any XML
     * deserialization based on its annotations. Values that are
     * references could be substitutes objects of existing ones.
     *
     * @return this returns true if the object is a reference
     */
    public boolean isReference() {
        return value.isReference();
    }
}
